This invention relates generally to systems, apparatuses and methods for bringing to the surface liquids contained in underground reservoirs. Specifically, the invention relates to systems, apparatuses and methods for creating a geyser-type flow and controlling it in such a way as to safely bring to the surface liquids contained in a reservoir.
A plunger pump reciprocated by a pump jack (or beam pumping unit) is the typical means used to extract liquid hydrocarbons (“oil”) from an underground reservoir when the well can no longer naturally flow. However, pump jacks can have difficulty extracting oil from high gas-oil-ratio (GOR) reservoirs or from wells deeper than 10,000 ft.
Gas lift is an artificial-lift method used for high production rate wells (i.e., typically 2,000 barrels per day or greater) in which gas is injected into the well tubing to reduce the hydrostatic pressure of the liquid column, thereby permitting liquids to enter the tubing at a higher flow rate. Typically, the injected gas is conveyed down the annulus located between the tubing and the well casing and enters the tubing through a series of gas-lift valves located at different depths along the length of tubing. A packer must be positioned at the bottom of the casing-tubing annulus in order to isolate the annulus from the bottom end of the tubing. Gas injection continues as the liquids flow at the desired rate.
While gas lift is desired in certain down hole applications, “severe slugging” (or “heading”) is not desired in any application. Severe slugging occurs when gas continues to accumulate in a reservoir cavity or in the casing-tubing annulus, with the liquid level rising in the well tubing. As gas pushes down the liquid level in the annulus and enters the tubing, the tubing hydrostatic pressure is reduced, thereby creating a lower downstream pressure. Expansion of the gas then provides the driving force to rapidly expel the liquid, along with the gas, out of the well.
Because catastrophic consequences to operators and severe damage to downstream facilities can occur during a severe slugging event, professionals in the field take measures to detect severe slugging and prevent it from occurring. This is one reason, for example, why gas lift makes extensive use of valves and chokes to stabilize the injection rate.
However, severe slugging has properties which can be useful for extracting oil from medium productivity wells (which can produce several hundred barrels per day) and from low productivity wells, such as those commonly labeled as stripper wells. A stripper well is usually defined as any oil or gas well which produces an average of 15 or less equivalent barrels of oil and gas per day. Therefore, a need exists for a system, apparatus and method to intentionally create, and then control in a safe manner, a severe slugging event.